Tc-99m-MAG3 was synthesized, and biodistribution and blood clearance rate were compared with those of 131I- OIH in mice and rats respectively. Finally renal image was obtained from a normal male volunteer before and after prescription of probenecid. The results obtained were as follows: 1) The uptake of Tc-99m-MAG3 by kindey was higher than that of 131I-OIH in mice 10 mins after injection (n=6, p〈0.05), but slightly lower uptakes were found in all organs (kindney, blood, stomach, intestinge and liver) 2 hrs after injection. 2) For Tc- 99m-MAG3 t½α=2.4±0.0 min, t½β=44.3±7.4 min, and blood clearance=3.4±0.5 ml/min, and for 131I-OIH t½α=1.8±0.2 min, t½β=69.1±9.5 min, and blood clearance=1.3±0.1 min were found in rats. 3) From the renogram of normal male volunteer, we could find that tmax=130 sec and t½=430 sec before probenecid prescription, and tmax=150∼170sec and t½=810∼1,170 sec after probenecid prescripron. From these results we concluded that Tc-99m-MAG3 can be used instead of 131I- OIH for obtaining renal image.